Current stereo imaging systems that contain a roof prism (bi-prism) may have imaging aberration issues. With reference to FIG. 1, note that a great amount of optical rays can proceed through each roof segment of a roof prism (only the rays for one of the two roof segments is shown to avoid drawing clutter). Some of these rays will cause image degradation at the image plane.
FIG. 1 is a schematic representation of a stereoscopic optical system 10. It is to be noted at the outset that the existing optical system 10 can have a roof prism 12. However, the existing optical system 10 is of a single aperture optics design and thus can have at least some issues and/or challenges. For example, it is possible for the existing optical system 10 to have an imaging aberration issue. A first issue, imaging aberration, can include color separation, astigmatism and/or field curvatures that can be difficult to correct due to the roof prism nature. A second issue can be that the stereo image separation might be limited by a prism angle and a small envelope size of a borescope or endoscope camera. A third issue can be that the stereo imaging is very sensitive to optical component position deviations from perfection (i.e., tolerances). Such deviations can include axis decentering and/or tilt, and are especially of concern regarding the roof prism position.
An optical system 10, such of that illustrated in FIG. 1 can include an image member 14 located at a position along a center optical axis 16 and a first stereoscopic image area 18 on a first side of the optical axis for receipt of a first stereoscopic image thereon. The system can have a second, separate stereoscopic image area 20 on a second, separate side of the optical axis for receipt of a second, separate stereoscopic image thereon. In the FIG. 1, these are shown in an up and down orientation, but could be translatable to left and right orientation. The image member 14 can be or can at least include an image window (also indicated via reference numeral 14) that has an image plane 22 that contains the first and second image areas 18 and 20. The image plane 22 can be at the right-most surface of the image member 12 as viewed within FIG. 1. The image member 14 could also include an image capturing element, such a charge-coupled display (CCD), etc. The specifics of the image member 14, the possible components contained therein, etc. are not needed for understanding aside from the two stereoscopic image areas 18 and 20 can be present at the image plane 22.
The optical system 10 of FIG. 1 can include an optical arrangement 24 that extends along the center optical axis 16. Proceeding from left to right within FIG. 1 and along the optical axis 16, the overall optical arrangement 24 can include a first window 30, the roof prism 12, a first lens 34, a second lens 36, a second window 38, a third window 40, a third lens 42, a fourth lens 44 and a fifth lens 46. The first window 30, the roof prism 12, the first lens 34, the second lens 36, and the second window 38 may be grouped together as first portion of the optical arrangement. The third window 40, the third lens 42, the fourth lens 44, and the fifth lens 46 may be grouped together as a second portion of the optical arrangement. The first portion may be detachable from the second portion, with at least some of the windows (i.e., first-third windows, 30, 38 and 40) providing boundaries from the outside environment. Such boundaries can provide a barrier to prevent outside influences (e.g., dirt, moisture, etc.) from engaging portions of the optical arrangement (e.g., the lenses). Moreover, it is to be appreciated that the second window 38 can include a single aperture 48 that is to be centered upon the optical axis 16.
The roof prism 32 can have first and second roof segments 50, 52 and an apex 54 that is to be located on the optical axis 16. Within FIG. 1 only rays passing through the first roof segment 50 are shown so as to avoid clutter within the Figure and to allow ease of review and discussion about the issues and concerns regarding the rays passing through the first roof segment. It is to be understood that different rays may be passing through the second roof segment 52 and that similar issues, concerns are present.
With attention to the rays passing through the first roof segment 50, it should be noted that except for the single aperture 48 at the second window 38, which is to be centered on the optical axis 16, there can be limited qualification regarding the passage of the rays through the remainder of the system 10 and to the image plane 20. At least some of the rays cause the noted degradation of the image. Examples of image degradation include undesirable color separation, undesirable contrast, undesirable contrast, image size distortion, image shape distortion, vignetting, etc. It is to be noted that it can be possible for rays to pass through various portions of the lenses that cause or otherwise affect image degradation. Also, recall that the single aperture 48 can be present. As such, both of the two sets of rays for the two images at the images areas 18, 20 must pass through the single aperture 48. With FIG. 1 providing a background, there is a current need for improvements concerning stereo imaging systems, and specifically such stereo imaging systems within borescopes and endoscopes.